DescEnd will be clipped for alignment in CoreFindFreePagesI, and it
may fall below DescStart, when alignment is more than 16KB (included)
and both DescStart and original DescEnd fall into a single range of
such alignment. This results in a huge size (Negative number in
unsigned type) for this descriptor, fulfilling the allocation
requirement but failing to run ConvertPages; at last it causes
occasional failure of AllocatePages.
A simple comparison is added to ensure we would never get a negative
number.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Heyi Guo <heyi.guo@linaro.org>
Reviewed-by: Liming Gao <liming.gao@intel.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17575 6f19259b-4bc3-4df7-8a09-765794883524
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